This invention relates generally to a fork lift truck with a lifting frame, a rear weight and a driver""s cab. The lifting frame, on which a load receptacle device is mounted so that it can be moved vertically, is located on the front end of the fork lift truck. On the rear end of the fork lift truck there is a rear weight that acts as a counterweight for the weight of the load receptacle and for the inertial forces of the load being lifted with the load receptacle device.
On fork lift trucks of the prior art, there is a vehicle frame between the lifting frame and the rear weight. The lifting frame is generally mounted on the vehicle frame so that it can pivot, whereby the forces and moments that are exerted on the lifting frame are supported by the vehicle frame. The vehicle frame is also rigidly connected with the rear weight. The forces that occur between the lifting frame and the rear weight are therefore transmitted via the vehicle frame. In many cases, the rear weight is a component of the vehicle frame, i.e., it is integrated into the vehicle frame. On fork lift trucks of the prior art, the driver""s cab conventionally forms a separate component and is attached to the vehicle frame with damping elements. The components of the driver""s cab frequently include a protective roof, and on a closed driver""s cab, windows and doors. On fork lift trucks of the prior art, both the frame and the driver""s cab are realized in the form of welded structures, and are complex and expensive in terms of their manufacture and transport. Therefore, it is an object of this invention to provide a simply constructed fork lift truck that can be manufactured easily and economically.
The invention teaches that the driver""s cab of the industrial truck forms a load-bearing component of the, truck wherein there are preferably at least two bearings for the lifting frame that are at a substantially vertical distance from one another, by means of which the lifting frame is connected to the driver""s cab in a force-transmitting connection. The forces that act on the lifting frame are transmitted at least partly via the driver""s cab. These forces are absorbed directly or indirectly by the driver""s cab at preferably two bearings. The driver""s cab thus acts as a force-transmitting component and performs at least partly the force-transmitting function of the vehicle frame, which in the prior art is realized in the form of a separate component. This construction leads to a self-supporting structure of the fork lift truck, in which no significant load-bearing components are necessary besides the vehicle frame.
The bearings can be realized, for example, in the form of rigid connections or in the form of rocker bearings, whereby the use of rocker bearings that have one rotational degree of freedom and/or that have two rotational degrees of freedom is possible. It should be noted that in connection with this invention, two or more connections or rocker bearings oriented coaxially with one another, which are separated from one another only in the transverse direction of the fork lift truck, should be considered as belonging to a single bearing.
In one embodiment of the invention, in the vicinity of a bearing for the lifting frame, preferably in the vicinity of an upper bearing, at least one hydraulic cylinder is located between the lifting frame and the driver""s cab. The hydraulic cylinder can thereby be fastened on one hand to the bearing of the driver""s cab and on the other hand to the lifting frame. The lifting frame can be tilted by changing the length of the hydraulic cylinder, i.e., by extending or retracting the piston.
Each bearing for the lifting frame is suitable for the transmission of compression forces or tension forces. For this purpose, there is at least one rocker bearing at each of these bearings. Torques that are originated from the lifting frame are absorbed by the two separated bearings of the driver""s cab.
The driver""s cab also has at least one bearing for the rear weight, by means of which the rear weight is connected directly or indirectly with the driver""s cab. The driver""s cab thus connects the rear weight with the lifting frame. The bearing for the rear weight is preferably located on an upper portion of the rear weight. The driver""s cab, when realized in accordance with the invention, thus extends into the area above the rear weight. The bearing for the rear weight is appropriately designed for the transmission of forces and moments. For this purpose, the driver""s cab and the rear weight can be fastened to one another by means of threaded fasteners.
The driver""s cab has at least one strut that extends between the lower bearing for the lifting frame and the bearing for the rear weight. Compression and tension forces are thus transmitted directly between these two bearings by means of this strut.
The driver""s cab also has a framework construction, by means of which forces can be transmitted between the upper bearing for the lifting frame and the bearing for the rear weight. Because it is necessary to make sufficient space available for the driver inside the driver""s cab, no continuous linear struts can be provided in this location. Instead, the framework construction is provided for the transmission of forces.
The framework construction advantageously forms a triangle, in which a first corner of the triangle is located in the upper portion of the driver""s cab, and a second and third corner of the triangle are located in the vicinity of the bearing for the rear weight. The forces that originate from the upper bearing for the lifting frame are transmitted directly or indirectly, e.g., by means of an additional strut, into the upper corner of the triangle, the two other corners of which are supported on the rear weight.